Phytoplasma etiology and epidemiology of wheat streak and stunting disease in Central India.

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A total of 151 genotypes of durum and bread wheat exhibiting symptoms of stunting and bushy growth, leaf yellowing, and drying of clumps were recorded at ICAR-IARI Regional Station, Indore, Madhya Pradesh, India from 2016 to 2018. The disease incidence was recorded more in durum wheat genotypes as compared to bread wheat genotypes. The presence of any virus, bacterial, and fungal pathogens was ruled out by applying cultural growth and electron microscopy. However, association of phytoplasmas presence was confirmed in 142 (out of 151) durum and bread wheat genotypes by employing PCR primer pairs of 16S rRNA, S and A genes. The sequence analysis of all the genes and in silico RFLP analysis of 16S rDNA sequences of wheat phytoplasma strains identified them as rice yellow dwarf group (16SrXI-B) and Bermuda grass white leaf group (16SrXIV-A). Two symptomatic weed species ( and ) tested positive for 16SrXI-B phytoplasma subgroup and four weed species (, , and ) for 16SrXIV-A phytoplasma subgroup growing in and around wheat fields. Six hopper species identified from symptomatic wheat fields were also analyzed for phytoplasma presence. Three hopper species viz., , , and were tested positive to phytoplasmas in 16SrXIV group, while , , and tested positive to 16SrXI group of phytoplasmas in nested PCR assays. Transmission assays revealed that and successfully transmitted the 16SrXIV-A strain from infected wheat to healthy wheat plants; however, was able to transmit 16SrXI-B subgroup from infected wheat to healthy wheat plants under glasshouse conditions. A variation in phytoplasma associated disease incidence was recorded on wheat genotypes in different years and was also found positively correlated with temperature, humidity, and hopper population. The identification of similar phytoplasma strains (16SrXI and 16SrXIV group) from wheat, weeds, and hoppers indicated potential risk of transmission of these strains to wheat genotypes and other agricultural crops, which needs further investigations on epidemiological aspects.

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The online version contains supplementary material available at 10.1007/s13205-024-04114-3.